Induction coil



June 2, 1931. i.. GRIFFITHS ET AL v 1,808,548

INDUCTION CQ'IL Filed April 15. 1930 Invetois: Leonard Griffiths Cecil J. Morton,

bg wf/ Their Attorneg.

Patented June '2, 1931 UNITED STATES PATENT OFFICE LEONARD GRIFFITHS AND CECIL J'. MORTON, OF COVENTRY, ENGLAND, ASSIGNOBS T0 GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK INDUCTION con.

. Application illed AprilA 15, 1930, Serial No. 444,570, and in Great Britain November 29, 1929.

Our invention relates to induction coils such as used, for example, in ignition systems of internal combustion engines.

Induction coils, as heretofore constructed, have ordinaril been made with a fixed core structure. I these induction coils are designed for obtaining the most satisfactory spark discharges for operation in an ignition system requiring a small number of spark discharges per minute such, of example, as a single cylinder engine, they do not produce the moet satisfactory spark discharges when used on a' higher speed engine, or a multi-cylinderengine, requiring a large number of sparks per minute. This is due to the fact that the time constant of the coil permissible to produce the most satisfactory spark discharge where a small number of sparks per minute are required is obtained by making the time constant of the windings of the coil large, and if the coil is used under conditions requiring a considerably larger number of sparks por minute, the time constant of the windings is not such as to produce the most satisfactory spark.

The object of our invention is toY produce an induction coil in which the time constant of the windings is adjustable to adapt the coil for use in different ignition systems requiring a widely differing number of sparks per minute. We would accomplish this by providing an induction coil having primary vand secondary windings which are arranged specification.

In the drawin s Fig. 1 is a longitudinal section of an in uction coil embodying our invention, and Fig. 2 is aI section on the line 2--2 of Fig. 1.

Referring to the drawings, the induction coil, which we have illustrated as an example of one manner of carrying out our invention, includes the soft iron-wire core 10 having a primary winding 11 wound thereon between an insulating sleeve 12 closely fitting the core 10 and terminating a short distance from the ends thereof and an insulating sleeve 13 surrounding the primary winding 11 and extending the entire length of the core 10. The secondary windings 14 and 15 -of the coil are arran ed on the sleeve 13. These secondary win ings are retained in place by insulating sleeves 16 and 17 which are separated by an insulating spacing ring 18 arranged on the sleeve 13. The primary and secondary windings of the induction coil are secured within a cylindrical insulating casingk 19 by end-caps 20 and 21 of molded insulating material which are fitted on the sleeve 13 and inside of the cylindrical casing 19, the entire structure being secured together by a bolt 22 extending through the core 10 and the end-caps. The secondary windings 14 and 15 of the induction coil are connected in series between terminals 23 which are molded in the end-caps. Laminated magnetic segments 24 extend from the ends of the lcore 10 to the cylindrical casing 19 and are preferably retained in lace by molding them in the insulating endlcaps 20 and 21. It will 'be observed that the core 10 of iron wires and the laminated magnetic segments 24 constitute a U-shaped core structure within the casing 19 in which the primary and secondary windings of the induction coil are arranged between the arms of the U.

In order to vary the time constant of the windings of the induction coil, that is to say, the ratio of the-inductance to the resistance of the windings, we arrange a laminated magnetic core member 25 across the magnetic segments 24 to complete the m netic circuit including the core 10, magnetic segments 24 and magnetic core member 25 so as to vary the reluctance of the flux path through the core structure of the induction coil. We prefer to adjustably secure the core member 25 to the casing 19 by clamping bands 26 which extend about the casin and are bolted to the core member as indicated tol supp at 27 The induction coil ma be supported in any convenient manner, ut weneer ort the same on feet 28 whic are bolted to the magnetic member 25 at 29. By this arrangement, upon loosening the bolts 27 We can move the casing 19 and endcaps 21 with respect to the magnetic core member 25 so as to vary' the air gap between the segments 24 and the core member, which .is greatest when the casing 19 and the endcaps 20 and 21 are' turned't'e'bring the magnetic segments intothe fposition indicated at`24 in Fig. 2, which is the farthest from the magnetic core member.

When our induction coil is to vbe used in an ignition system requiring a small number of sparks per minute we adjust the-casy in 19 in the end-caps 20-and 21 so as to brlng the magnetic segments 24 into alinement with the magnetic core structure 25, as shown in full lines in Fig. 2. This gives a maximum time constant for the windings of the induction coil-and gives the most satisfactory spark under those conditions. When the` induction coil is usedin an ignition system where the reater number of spark discharges per minute are required, t e time constant of the induction coil is ad- -usted to a lower value, and this can readily e accomplished by loosening the bolts 2 and turning the casing 26 and the end-caps 20 and 21 so as to move the magnetic segments 24 out of alinement with the magnetic core member 25 and increase the air gap between them. ln this adjusted posi-V tion the coiljwill operate more satisfactorilyl when it is required to supply a. higher number of. sl arkdischarges per minute.

Modi cations of the .structure which5we have described will occur to those skilled in said core, a casing surrounding said core and said windings, magnetic segments extendin outwardly from said core, end-caps secure to said casing for retaining said segments in place, and means including a magnetic core member secured to said casing and adjustable with respect to said segments for varying the time constant o saidwindings.

4. An induction coil having acore, primary and secondary windings arranged on said core, a cylindrical casing surrounding said core and said windings, end-caps secured to said casing having magnetic segments attached thereto, and a magnetic core member secured to the outside oifsaid casing and adjustable with respect to said segments tor varying the time constant of said windings. l

In witness whereof, we have hereunto set our hands this twenty-sixth day of March,

LEONARD GRFFITHS. CECL MORLIQN.

the art so that we do not desire our invenl 'tion to be limited thereto, and we intend in the appendedclaims to cover all 'modifications w ich do not depart from the spirit and scope of our invention.

' vWhat we clalm as new and desireto secure by Lett ers Patent of the United States 1. An magnetic core, primary and secondary windings arranged between the arms of said U-shaped core, and a vmagnetic core member extending across the arms` of said ti-shaped.- core and adjustable about the axis of said windings to vary the time constant thereof.

induction coil having a. iii-shaped I 2. An induction coil-.having a core, primary and secondary windin arranged about said core, a casin enclosing said core and said windings, an means including, a magnetic core membersecured to said casing andadjustable with respect thereto for varying the time constant of said windings.

3. An induction coil having a. core, ri-q 

